To assess the quality of surface water both spatially
and temporally at selected stream sites representing different land
Relate observed surface-water quality to different land-use settings.
Sampled 12 fixed sites monthly for targeted physical
and chemical data. Additional samples were collected during high flow
events or during irrigation season.
March 1993 through September 1995
Targeted Physical and Chemical Data:
Flow, specific conductance (salinity), continuous
temperature data, major ions, nutrients, pesticides, dissolved organic
compounds (DOC), suspended organic carbon (SOC), and suspended sediment.
Surface-water quality generally is better in forested
mountain areas than in other land uses. Water quality in the agricultural
areas of the basin was the most degraded, primarily salinity and suspended
Pesticides frequently have been detected in surface
water in the urban setting, and several pesticides have been detected
throughout the agricultural areas of the basin during the growing
season. Although concentrations of individual pesticides generally
were low compared to established criteria, the ecological and human-health
effects of long-term exposure to pesticide mixtures are unknown.
The average number of pesticides detected in surface-water
samples was greater in mixed land-use areas than in land-use settings
that were primarily urban or agriculture.
Nutrient concentrations in urban streams have many
potential sources and generally were highest immediately downstream
from wastewater treatment plants.
Ground water (subsurface irrigation return flow) was
a major nonpoint source of nitrate, dissolved solids, and pesticides
(atrazine and prometon) in the lower reaches of the South Platte